Existing bearing seals are classified into two categories, contact seals and non-contact seals. A general standard to evaluate the performance of a bearing seal includes the seal's ability to prevent external contaminants from entering into the bearing and to prevent lubricating agent in the bearing from leaking out.
The contact seals have reliable sealing performance, but are not suitable for bearings in high-speed rotation. The reason lies in that: when a bearing rotates at high-speed, a large friction torque is produced between a sealing structure and other parts of the bearing, which not only generates large amount of heat to accelerate aging of the sealing structure, but also cause severe wear to the sealing structure. As a result, service life of the sealing structure is reduced.
The non-contact seals are suitable for providing sealing for bearings in high-speed rotation, but do not have satisfactory sealing performance.
Existing bearing seals can realize either a contact seal or a non-contact seal. However, advantages of both the contact seal and the non-contact seal can not be achieved at the same time, which is exactly contrary to expectations of some bearings applied in situations with high demanding for sealing (e.g., a motor driven hub bearing).